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Application of correction protocol in laryngeal cancer using kV

VIEWS: 3 PAGES: 11

  • pg 1
									    Application of 3D correction
    protocol in laryngeal cancer
         using kV-imaging


                            Anne Gangsaas
                       Technologist Erasmus MC
                       Daniel den Hoed Rotterdam




Outline

 Treatment protocol
 MV imaging
 kV imaging protocol
 Vocal Cord Study
 Future




                                                   1
Treatment protocol

T1 Laryngeal cancer patients
     33 x 2 Gy, 6 fractions weekly,
     2 lateral opposed fields


LRFS* 95%                         (1999-2005, n= 190)
P. van Rooij, unpublished QoL


22,3% patients with moderate voice handicap (≥30)
S. Osman Estro 2007, thesis accepted Radiotherapy Oncology




* Local Relapse Free Survival




Treatment protocol




                                                             2
Treatment protocol

Position verification (on linac)


   No protocol, first fraction MV imaging
   (until January 2008)



   No setup error correction, only isocenter
   verification




MV imaging
 First fraction only
    Translation > 5mm → next fraction imaging (vertebrae)




                                                   6MV, EPID
                                                  TheraView-NT ®




                                                                   3
  kV imaging

    Vertebrae + thyroid cartilage
    visible




   100 kV , EPID
    X-ray Volumetric Imaging (XVI)




  Protocol T1 laryngeal cancer
    kV No Action Level (NAL) protocol   (since February 2008)
    Match structure: thyroid


                                     Fraction 1-3 kV imaging
                                     → 3D correction
                                     Fraction 4 kV imaging
                                     → correction verification
                                     Weekly imaging (test phase)
Gantry angle 20-30º        and 90º   → verification




                                                                   4
Protocol T1 laryngeal cancer
kV imaging




                               Gantry angle 30º
                               kV Image made on Elekta with XVI,
                               S20 diaphragm, 100 kV, 5 frames, EPID




Protocol T1 laryngeal cancer
Matching on thyroid contours




Gantry angle 30º                DRR made in Focal

TheraView-NT ®




                                                                       5
Protocol T1 laryngeal cancer
Translation




    Translation X direction



Gantry angle 30º                DRR made in Focal
TheraView-NT ® , 100kV, EPID




Protocol T1 laryngeal cancer

kV imaging




                               Gantry angle 90º
                               kV Image made on Elekta with XVI,
                               S20 diaphragm, 100 kV, 5 frames, EPID




                                                                       6
 Protocol T1 laryngeal cancer
 Matching on thyroid contours




Translation Y and Z direction (kV90)
Translation X direction       (kV30)

            → 3D correction


  Gantry angle 90º                     DRR made in Focal
  TheraView-NT ® , 100kV, EPID




 Swallowing



                                        Movement of thyroid cartilage
                                                                        (few frames)


                                          “No swallowing” instruction



                                         Gantry     start angle 260˚
                                                    stop angle 100˚
                                         100kV, 361 frames (1 frame/ 0,5˚)
                                         S20 diaphragm
                                         Medium resolution reconstruction
CBCT made on Elekta with XVI




                                                                                       7
Protocol T1 laryngeal cancer
Matching on vertebrae contours (swallowing)




  Gantry angle 90º                    DRR made in Focal
  TheraView-NT ®




 MV vs. kV                MV imaging kV imaging
 Dose                     0 Gy                0,14 mGy
                                              (first 4 fractions)
 Visibility               Vertebrae           Vertebrae +
                                              Thyroid cartilage
 Imaging time             0 minutes           2 minutes
 Matching time            3 minutes           3-5 minutes*


 * will be shorter through practice




                                                                    8
Vocal Cord Study (VCS)




 Picture presentation S. Osman Estro 2007




Vocal Cord Study (VCS)

 Goal VCS
           single cord radiation T1 laryngeal cancer


                         position verification!
 Clinic
           treatment as non- VCS patients:
                          33 x 2 Gy, 6 fractions weekly, 2 lateral fields
                          kV NAL protocol
           research: daily CBCT, bi-weekly 4D CT scan




                                                                            9
Future verification
 3D online protocol with CBCT automatic match (thyroid cartilage)




Future

 Difficulties
     Data storage in XVI
     (Multiple) structure registration (clip box)


 VCS → data for other H&N sites (verification):
     tumor site → match structure → PTV margins (IMRT)




                                                                    10
Thank you!

Questions?




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